Gas turbine engine with selective flow path

ABSTRACT

A method of operating a gas turbine engine includes generating a flow of combustion products from a gas turbine generator that has a gas generator axis of rotation. A duct is oriented in a first position to direct the flow of combustion products that have passed over at least one gas generator turbine rotor through a fan drive turbine in response to a first desired flight condition. An axis of rotation of the fan drive turbine is transverse to a gas generator axis of rotation. The duct is oriented in a second position to direct the flow of combustion products that have passed over at least one gas generator turbine rotor through an augmentor section in response to a second desired flight condition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 14/713,187 filed May 15, 2015, which claims priority to U.S. Provisional Patent Application No. 62/001,882, filed on May 22, 2014.

BACKGROUND OF THE INVENTION

Gas turbine engines are known and typically include a fan delivering air as bypass air into a bypass housing and further delivering air into a core engine. Air in the core engine is directed into a compressor where it is compressed. The compressed air is then delivered into a combustion section where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors, driving them to rotate.

Recently, it has been proposed to increase the diameter of the fan to, in turn, increase bypass ratios, or the volume of air delivered as bypass or propulsion air compared to the volume of air delivered into the core engine. However, the ability to make this increase is somewhat limited by the packaging envelope available on an aircraft.

It has been proposed to replace a single large diameter with a plurality of fan rotors. However, the proposals for driving the plurality of fan rotors have deficiencies in general.

SUMMARY OF THE INVENTION

In one exemplary embodiment, a method of operating a gas turbine engine includes generating a flow of combustion products from a gas turbine generator that has a gas generator axis of rotation. A duct is oriented in a first position to direct the flow of combustion products that have passed over at least one gas generator turbine rotor through a fan drive turbine in response to a first desired flight condition. An axis of rotation of the fan drive turbine is transverse to a gas generator axis of rotation. The duct is oriented in a second position to direct the flow of combustion products that have passed over at least one gas generator turbine rotor through an augmentor section in response to a second desired flight condition.

In a further embodiment of the above, the gas generator includes at least one compressor rotor, at least one gas generator turbine rotor and a combustion section.

In a further embodiment of any of the above, the first desired flight condition is subsonic flight.

In a further embodiment of any of the above, the second desired flight condition is supersonic flight.

In a further embodiment of any of the above, the flow of combustion products passes over at least one gas generator turbine rotor prior to entering the duct.

In a further embodiment of any of the above, the fan drive turbine drives a shaft and the shaft engages gears to drive at least two fan rotors.

In a further embodiment of any of the above, at least two fan rotors include a variable inlet and a variable outlet. The variable inlet and the variable outlet are in an open position when the duct is in the first position and in a closed position when the duct is in said second position.

In a further embodiment of any of the above, the augmentor section includes a variable exhaust. The variable exhaust is in a closed position when the duct is in the first position and in an open position when the duct is in the second position.

In a further embodiment of any of the above, an axis of rotation of the gas generator is generally perpendicular to an axis of rotation of the shaft.

In a further embodiment of any of the above, an axis of rotation of the gas generator is generally coaxial with an axis of rotation of at least two fan rotors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a gas turbine engine.

FIG. 2 is a front view of the FIG. 1 engine.

FIG. 3 shows a first embodiment in a first configuration.

FIG. 4 shows the first embodiment in a second configuration.

FIG. 5 shows a dual configuration of FIG. 3.

FIG. 6 shows a dual configuration of FIG. 4.

DETAILED DESCRIPTION

A gas turbine engine 20 is illustrated in FIG. 1 having a gas generator 22. The gas generator 22 may be a two spool gas generator having a low speed spool in which a first upstream compressor rotor 24 driven by a downstream or low pressure turbine rotor 26. A high speed spool includes a high pressure compressor rotor 28 rotating with a high pressure or upstream turbine rotor 30. A combustion section 32 is positioned intermediate rotors 28 and 30.

An exhaust duct 34 is positioned downstream of the gas generator 22 and receives products of combustion which have driven the turbine rotor 26 to rotate. These products of combustion pass across a fan drive turbine 36 mounted in a housing 37. The fan drive turbine 36 drives a single shaft 38 that engages a plurality of bevel gears 40 to, in turn, drive shafts 41 associated with fan rotors 42, 44, 46 and 48. Each of the fan rotors 42, 44, 46 and 48 are mounted within separate housings 50.

By providing the single shaft 38, which drives at least four fan rotors and by utilizing a fan drive turbine 36 which is positioned downstream of the last turbine rotor 26 in the gas generator 22, this disclosure provides compact packaging, while still providing adequate drive for the fan rotors 42, 44, 46 and 48.

FIG. 2 is a front view of an aircraft wing 80, which may mount an engine such as engine 20. As shown, the gas generator is associated with the housing 37. The fan rotors 42, 44, 46 and 48 have diameters that are not unduly large, such that they fit within the packaging window of associated wing 80.

The basic engine as described above is disclosed in co-pending U.S. patent application Ser. No. 61/989,675, entitled “Gas Turbine Engine With Distributed Fans,” filed on May 7, 2014. This basic fan structure can be incorporated into a gas turbine engine arrangement having one or more gas generators, and paired sets of the distributed fan.

As shown in FIGS. 3 and 4, a fan set 130 includes an engine 100 having a gas generator 102 for driving a fan drive turbine 104 or an augmentor 106. Products of combustion from the gas generator 102 are directed to the fan drive turbine 104 or the augmentor 106 by a moveable duct 108. An exhaust path when the moveable duct 108 is directed to the fan drive turbine 104 is generally perpendicular to an exhaust path when the moveable duct 108 is directed to the augmentor 106. In this embodiment, the moveable duct 108 is a three bearing swivel duct. However, other ducts capable of directing the products of combustion from the gas generator 102 to the fan drive turbine 104 and the augmentor 106 could be used.

When the gas generator 102 is used to drive the fan drive turbine 104 as shown in FIG. 3, products of combustion from the gas generator 102 pass into an exhaust duct 110. A shaft 112 rotates about an axis Y, while the gas generator 102 rotates about an axis X. The axis X is generally perpendicular to the axis Y. Shafts 114 are driven by shaft 112 to turn fan rotors 116 and 118. The shafts 114 extend in a direction generally parallel to the axis X and perpendicular to the axis Y. Although the shaft 112 is shown turning two separate rotors 116 and 118, additional rotors could be turned by the shaft 112.

A variable inlet 120 surrounds an inlet to the rotors 116 and 118 and a variable outlet 122 surrounds an outlet of the rotors 116 and 118 and the exhaust duct 110. When the moveable duct 108 engages the drive turbine 104 to turn the rotors 116 and 118, the variable inlet 120 and the variable outlet 122 are in an open position and an augmentor outlet 128 is in a closed position to reduce drag.

When the gas generator 102 is used to drive the augmentor 106, the augmentor outlet 128 is opened and products of combustion from the gas generator 102 pass into an augmentor duct 126. The variable inlet 120 and the variable outlet 122 close to reduce drag.

Fuel spray rails 124 extend into the flow path formed by the augmentor duct 126 to inject fuel which is ignited by an igniter 125 to produce an afterburner effect from the augmentor 106.

FIG. 5 shows an arrangement using the two fan sets 130 with the moveable duct oriented to drive the fan drive turbine 104. Utilizing the two fan sets 130 in this orientation creates a higher propulsive efficiency with lower fuel consumption and exhaust temperatures for long range cruise situations.

FIG. 6 shows an arrangement using the two fan sets 130 with the moveable ducts 108 oriented to engage the augmentors 106. Utilizing the two fan sets 130 in this orientation allows for supersonic or elevated speeds of travel with a higher fuel consumption than the arrangement shown in FIG. 5.

The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims. 

The invention claimed is:
 1. A method of operating a gas turbine engine comprising: generating a flow of combustion products from a gas turbine generator having a gas generator axis of rotation; directing said flow of combustion products to pass over at least one gas generator turbine rotor and into a duct; orienting said duct in a first position to direct said flow of combustion products through a fan drive turbine in response to a first flight condition, wherein an axis of rotation of said fan drive turbine is substantially perpendicular to said gas generator axis of rotation and said first flight condition is subsonic flight, said fan drive turbine driving at least two fan rotors, wherein said gas generator axis of rotation is substantially parallel with respective axes of rotation of said at least two fan rotors; and orienting said duct in a second position to direct said flow of combustion products through an augmentor section in response to a second flight condition, wherein said second flight condition is supersonic flight.
 2. A method of operating a gas turbine engine comprising: generating a flow of combustion products from a gas generator having a gas generator axis of rotation; directing said flow of combustion products to pass over at least one gas generator turbine rotor and into a duct; orienting said duct in a first position to direct said flow of combustion products through a fan drive turbine in response to a first flight condition, wherein an axis of rotation of said fan drive turbine is transverse to said gas generator axis of rotation, said fan drive turbine driving a shaft that engages gears to drive at least two fan rotors, wherein said gas generator axis of rotation is substantially parallel with respective axes of rotation of said at least two fan rotors; and orienting said duct in a second position to direct said flow of combustion products through an augmentor section in response to a second flight condition.
 3. The method of claim 2, wherein said gas generator further includes at least one compressor rotor and a combustion section.
 4. The method of claim 2, wherein said at least two fan rotors include a variable inlet and a variable outlet, said variable inlet and said variable outlet being in an open position when said duct is in said first position and in a closed position when said duct is in said second position.
 5. The method of claim 4, wherein said augmentor section includes a variable exhaust, said variable exhaust is in a closed position when said duct is in said first position and in an open position when said duct is in said second position.
 6. The method of claim 2, wherein said gas generator axis of rotation is substantially perpendicular to said axis of rotation of said fan drive turbine.
 7. The method of claim 2, wherein said flow of combustion products pass over a surface of said at least one generator turbine rotor.
 8. The method of claim 2, wherein said duct is a three bearing swivel duct.
 9. The method of claim 2, wherein each of said fan rotors are enclosed in a separate housing.
 10. The method of claim 2, wherein a variable housing surrounds an inlet to said at least two fan rotors.
 11. The method of claim 10, wherein said at least two fan rotors each include an outlet surrounded by a single variable outlet.
 12. The method of claim 11, wherein said fan drive turbine includes an exhaust duct having an exhaust duct outlet and said exhaust duct outlet is surrounded by said single variable outlet.
 13. The method of claim 11, said at least two fan rotors including a variable inlet, wherein said variable inlet and said single variable outlet are in an open position when said duct is in said first position and in a closed position when said duct is in said second position.
 14. The method of claim 2, wherein said first flight condition is subsonic flight and second flight condition is supersonic flight.
 15. The method of claim 2, wherein said gas turbine generator is a two spool gas generator and includes a low spool driven by a low pressure turbine and a high spool driven by a high pressure turbine, wherein said low spool drives a forward most compressor having a single outlet for providing compressed air to a high pressure compressor. 